Side effects often appear after patients have taken medicines, and one of the most common side effects is dyskinesia, which not only hinders a normal life, and may also induce a variety of symptoms of Parkinson's disease.
In addition to drug-induced side effects, after the drug has been taken for a long period of time, it may often lose efficacy and often induce an “on-off” alternating reaction. When the drug induces the “on” reaction, the patient's symptom is under control, but when the “off” reaction is induced, the patient's symptoms will not be able to be controlled, and thus the ability to lead a normal life is affected.
Therefore, when the patient cannot carry out normal activities or quality of life is affected due to the above two reasons (the side effects of drugs and the “on-off” alternating reaction), surgical treatments would need to be considered. Such surgeries can be divided into two main types: deep brain stimulation (DBS) and lesion procedure which involves a higher risk, among which deep brain stimulation is more popular.
In the current deep brain stimulation surgery, microelectrode recording (MER) is employed to help determine the implant position for a permanent wire that is used to stimulate the target within the brain by electricity. Specifically, this technique first uses Computed Tomography (CT) scanning and Magnetic Resonance Imaging (MRI) to search for a rough position of the target to obtain a first implantation trajectory for implanting a probe with a microelectrode recording sensor. This sensor performs microelectrode recording to confirm whether the probe has reached the predefined position of the stimulation target. If the first implantation of the probe position is not satisfactory, then the probe is taken out and implanted in a different trajectory, until the probe is successfully implanted in the predefined target position. When the depth of probe implanted has reached the stimulation target, the probe can then be removed and replaced with a permanent wire. However, the microelectrode recording technique can be used only to determine whether the depth of implanted probe has reached the stimulation target, but cannot be used to determine the exact location of the probe within the stimulation target. Therefore, it is possible that the permanent wire is placed at the non-optimal position within the stimulation target rather than being properly implanted at the “optimal location” within the stimulation target. If the placement position is not ideal for the permanent wire, the part of the target within the brain that is stimulated upon electrical conduction will be limited, and thus cannot achieve the desired effect of the surgery.
U.S. Pat. No. 6,301,492 discloses an integrated probe applicable to DBS surgery, which integrates a DBS wire into a probe with a microelectrode recording sensor, so that after the probe is implanted into the stimulation target, the probe is not removed and replaced by a permanent wire, this can reduce the complexity of the surgery. However, this prior-art technique still cannot determine if the implant position of the probe is accurate or not, so several trajectories for implanting the probe may still be required to locate the best implant position, so a fast and accurate implantation of the probe into the desired location of the stimulation target is not possible, which increases the burden on the patient and surgical risks of failure.
Referring to FIG. 1, an existing electrical impedance tomography (EIT) technique is shown. As shown, a wire with electrodes 1-16 is dispose around the periphery of a specific region 100. Through electrodes 1 and 3 on the surface of this specific region 100, a current source 104 may input signals into the specific region 100. In the meantime, the presence of a conductive target 102 will affect the electric field profile of 100, that is, the equipotential line 108 will be altered with the presence of 104 which reflects on the potential measured by electrodes 4-16 on the surface of the specific region 100. A voltage measuring device 106 is used for receiving signals to calculate the impedances within the specific region 100 and reconstruct the image of the conductive target 102 in the specific region 100. For example, the voltage measuring device 106 first connects to the electrodes 6 and 8, after receiving signals from the electrodes 6 and 8, it subsequently moves to measure voltage signals from other pairs of electrodes. In short, the electrical impedance tomography technique surrounds the target with electrodes, and performs some established voltage measuring procedures to delineate the location of the target within the region surrounded by the electrodes. As for DBS surgeries, it is different from the above technique in that the electrode is implanted into the brain toward the target. If one wishes to delineate the tissue structures surrounding of the probe in a DBS surgery so as to know the precise location of the probe implanted in the target, the electrical impedance tomography technique is not directly applicable.